1. Field of the Invention
The present invention relates to anisotropic conductive films used for electronically and mechanically bonding together electronic components, such as semiconductor components and circuit boards.
2. Discussion of the Related Art
To bond pins of a semiconductor component and circuits of a circuit board together, an anisotropic conductive film (ACF) generally is used. Generally, the anisotropic conductive film includes an insulative adhesive film and a plurality of conductive particles uniformly dispersed therein. In use, the anisotropic conductive film is compressed between the semiconductor component and the circuit board. The pins of the semiconductor component, in turn, are aligned with and face the circuits of the circuit board. Upon compression of the anisotropic conductive film, the conductive particles therein allow the pins of the semiconductor component to electrically connect the circuits of the circuit board. The adhesive film thus mechanically bonds the semiconductor component and the circuit board together, and the adhesive film further serves as an insulative overcoating, covering joint portions between the semiconductor component and the circuit board.
The conductive particles play an important role in bonding the semiconductor component and the circuit board together. Various conductive particles used in the anisotropic conductive film have also been developed. For example, an anisotropic conductive film is disclosed in U.S. Pat. No. 5,686,703. In this case, metal particles such as nickel particles, aluminum particles, and silver particles are used. Another anisotropic conductive film is disclosed in U.S. Pat. No. 6,042,894, displaying plastic particles coated with a metal film. Yet another anisotropic conductive film is disclosed in U.S. Pat. No. 6,451,875, in which macromolecule particles coated with a metal film are used.
However, sizes of above-mentioned conductive particles are at a scale of about a micrometer. The sizes of the pins/contacts of the semiconductor component and the circuits of the circuit board are very small. Therefore, an amount of the micrometer-scaled conductive particles that are compressed between pins/contacts of the semiconductor component and a corresponding circuit of the circuit board is limited. A contact interface between the pins/contacts of the semiconductor component and the corresponding circuit of the circuit board also is small. Thus, the anisotropic conductive film with micrometer-scale conductive particles generally cannot provide a satisfactory bonding between the semiconductor component and the circuit board.
What is needed, therefore, is an anisotropic conductive film with conductive particles that are configured for providing an improved bonding ability.